[Zapins]

Add about 3 grams of K2SO4 to each 10 gallons of water you have to bring up the K levels (brings K levels up to about 36 ppm).

Then for weekly dosing add roughly 1 gram per 30 gallons (this adds 4 ppm per dose).

Your plants will initially stockpile all the K they can in their tissues so the K levels will rapidly decrease from 35 to 0 ppm if you had to test. So you can probably be rather liberal with your first 2 dosings without K building up. Even when K does build up, it doesn't usually cause problems except in huge quantities (100's of ppms).

 

[Zapins]

Yes it is dry compound dosing.

I add the dry chemicals directly to the tank water. But you can pre-mix the chemicals before you add them with tank water if you want. The chemicals won't hurt the fish if you add them to the water directly, they try eat it, but spit it out when they realize it isn't food.

 

[Zapins]

I respectfully disagree, K does not block nutrient uptake in small amounts like 36 ppm (or even way higher concentrations). The recommended levels on the fertilator are mere guesses at what the K level should be, and do not indicate harmful levels at all. This is certainly not the case with other nutrients like Ca, Mg, N, etc... these nutrients will cause nutrient uptake problems if dosed in too high a concentration.

I started getting K blocking problems at about 500 ppm concentrations.

Also, K is not an easy element to test for, and is notoriously hard to measure accurately, so any test kits that are cheaply available for K (if there are any) are going to be very inaccurate. I took my water samples to a lab and had them vaporized and tested the spectral emissions.

There are only a few plants that are sensitive to higher K levels (1 or 2, by my count) and these are not very commonly kept.

It is always best to use test kits to determine the nutrient levels in our aquariums and dose accordingly like you suggested, but the test kits available for potassium won't be able to do this. I believe the best course of action is to read the plant signs and dose a relatively modest amount of K to ensure they get enough.

 

[Zapins]

Can you take pictures of the holes?

Sometimes plecos can cause small holes as they try rasp the leaves for algae. Also snails could possibly do the same, depending on what species you have.

The fact that your plants are missing leaves entirely seems more in line with herbivory.

What fish do you keep? What type of snails?

 

[Zapins]

That does look like herbivore damage. Potassium deficiency usually is accompanied by chlorosis of leaf tissue around the holes (yellowing tissue).

Seems like the most likely culprit is the snails. Apple snails you say? What species? These snails grow huge - up to a baseball in size. They are known to eat plants. Try take some better pictures of the snails, or look online for a positive ID.